LS7Roc

Minute after starting my car, the passenger side fan comes on then the other fan comes on. Sometimes I think both come on at the same time at startup and never shut off??

KNBlazer

are you saying they keep running while the car is running? one fan is controlled by a fan switch, the other is controlled by the ECM, and I am not sure but I think that one of the fans kicks on when you have your AC on... but not sure... I'm just trying to give you some ideas...

StevenB L98/LS1

the fan on the drivers side always runs, the 2nd fan comes on when the coolant temp sensor tells the ECM at a certain temperature to kick on (I believe 228 is the max temp the computer is set at that tells the second fan to kick on, when the car first runs through it heat cycle for the first time after being started, and yes the ac also kicks on the fan as well, makes the engine run a bit cooler.

LS7Roc

Yes, as soon as I start the car, one or both fans come on and stay running. Even with the car off and ignition on, passenger side fan comes on...

Theking

iTrader: (1)

The driverside fan should come on at approx 215-225 F (depending on wich PROM you have)

The passengerside fan is controlled either from AC Pressure switch or if the engine reaches ~238F (it will engage the secondary fan (passerngerside))

Regarding your issue have you changed something recently ? When did this problem occur first time. The fans shouldnt run all the time. Only if the temp is reached or if the AC pressure switch grounds it (when ON) the fan on driverside shouldnt come on unless it have reached the correct temp for it.

Both fans will run if you have used a paperclip to bridge the ALDL connector to view errorcodes, but when the paperclip is removed they shouldnt start.

You have to check your fan wiring to see if something is grounded. You have manual switches for the fans ? if yes, have the wiring for them checked and tested.

Theking

iTrader: (1)

Also a failing PROM can cause the fans to run constantly, but then the car would run bad or die sometimes. chugg etc.. when my EPROM went bad my fans kept running, replaced the PROM and it solved that problem (but first check your wiring and relays to the fans)

LS7Roc

How do I check the relays? The wiring seems okay, no tears or broken wires. Relays are clean.

norcalz28

iTrader: (13)

If a relay were to short internally it could be stuck in an on position, but this is highly unlikely, they tend to fail the other way, and not turn the fans on, which is what happened to me once.

1tpi

That's called limp home mode

Theking

iTrader: (1)

I know, didnt feel the need to write that in the first post :P